Wonder no longer!
New York artist Michael Mandiberg printed all of Wikipedia's articles and turned them into books - 7473 books to be exact. That's 7450 books more than Encyclopedia Britannica (23).
Wikipedia holds 50 Gigabytes of content which, at the time of Mandiberg's creation, contained 11,594,743 articles on 5,244,111 pages which covers subjects from "Aaaaa!" To "ZZZap!".
The collection can be yours for a mere $500,000 or $80 per volume. I guess Britannica still has Wikipedia beat on physical book cost.